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GI > The Liver As A Storage Organ > Flashcards

The Liver As A Storage Organ Flashcards

1
Q

What are the functions of the liver?

A

Carbohydrate metabolism
Fat metabolism
Protein metabolism
Hormone metabolism
Toxin/Drug metabolism and excretion
Storage
Bilirubin metabolism and excretion

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2
Q

Iron metabolism

A

Dietary iron is absorbed into the blood plasma by a transferrin

The iron is depositied in a number of different places, including myoglobin in muscles, iron in Hb in red blood ells, or stored in liver and reticuloendothelial macrophages

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3
Q

Ferritin

A

Large spherical protein consisting of 24 noncovalently linked subunits

Subunits form a shell surrounding a central core.

Core contains up to 5000 atoms of iron.

Ferritin found in the cytoplasm of cells but can also be found in the serum.

Concentration of ferritin is directly proportional to the total iron stores in the body

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4
Q

Ferritin excess

A

Can be due to excess iron storage disorders
Examples on slide 6

Can be due to non iron overload:
Liver disease
Some malignancies
Significant tissue destruction
Acute phase response (a protein that increases in response to acute condition):
-Inflammation
-Infection
-Autoimmune disorders
These lead to ferritin also rising

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5
Q

Ferritin deficiency

A

The only known cause of a low ferritin is iron deficiency

This can result in anaemia
-Ferritin less than 20 µg/L indicates depletion
-Ferritin less than 12 µg/L suggests a complete absence of stored iron.

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6
Q

Vitamins

A

Usually vitamins are provided in the diet.

Characteristic disorders when someone is vitamin deficient.

Recommended daily allowance (RDA)

Adequate intake (AI) where no evidence to determine RDA

Vitamins act as:
-Gene activators
-Free-radical scavengers
Coenzymes or cofactors in metabolic reactions

Excessive vitamin ingestion can result in toxicity

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7
Q

Water soluble vitamins

A

B and C

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8
Q

Fat soluble vitamins

A

A, D, E and K

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9
Q

Difference between fat soluble and water soluble vitamins

A

Water soluble vitamins pass more readily through the body, therefore, require more regular intake than fat soluble vitamins

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10
Q

Vitamin A (Retinoids)

A

Vertebrates ingest retinal directly from meat or produce retinal from carotenes (vegetables)

Requirements: 0.6 mg/day in men, 0.7 mg/day in women

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11
Q

Functions of Vitamin A

A

Vision:
-Used to form rhodopsin in the rod cells in the retina.

Reproduction:
-Spermatogenesis in male
-Prevention of foetal resorption of female

Growth

Stabilisation of cellular membranes

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12
Q

Vitamin A Deficiency

A

Rare in affluent countries as vitamin A levels drop only when liver stores are severely depleted.

Deficiency may occur due to fat malabsorption

Clinical Features:
-Night blindness
-Xeropthalmia
-Blindness

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13
Q

Vitamin A excess

A

Acute:
-Abdominal pain, nausea and vomiting
-Severe headaches, dizziness, sluggishness and irritability
-Desquamation of the skin

Chronic:
-Joint and bone pain
-Hair loss, dryness of the lips
-Anorexia
-Weight loss and hepatomegaly

Carotenemia:
-Reversible yellowing of the skin
-Does not cause toxicity

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14
Q

Functions of Vitamin D

A

Increased intestinal absorption of calcium

Resorption and formation of bone

Reduced renal excretion of calcium

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15
Q

Vitamin D deficiency

A

Demineralisation of bone:
-Rickets in children
-Osteomalacia in adults

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16
Q

Sources of Vitamin D

A

Fish and meat

Sunlight (7-dehydrocholestral)

25- hydroxyvitamin D3 is active version of vitamin D
1,25-dihydroxyvitamin D3 stored versions- maintains calcium balance in the body

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17
Q

Vitamin E stored in

A

Non-adipose cells such as liver and plasma – labile (widely available for use) and fixed pool (mobilised slowly)

Adipose cells – fixed pool

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18
Q

Function of Vitamin E

A

Important antioxidant

19
Q

Vitamin E requirements

A

4 mg/day in men
3 mg/day in women

20
Q

Causes of Vitamin E deficiency

A

Fat malabsorption (e.g. cystic fibrosis)
Premature infants
Rare congenital defects in fat metabolism e.g. abetalipoproteinaemia.

21
Q

Vitamin E excess

A

Relatively safe

22
Q

Vitamin K sources

A

Vitamin K is rapidly taken up by the liver but then is transferred to very low-density lipoproteins and low density lipoproteins which carry it into the plasma.

Sources:
Vitamin K1 (phylloquinone)
-Synthesized by plants and present in food

Vitamin K2 (menaquinone)
-Synthesized in humans by intestinal bacteria

Synthetic vitamin K’s:
-K3 (menadione)
-K4 (menadiol)

23
Q

Functions of Vitamin K

A

Vitamin K is responsible for the activation of some blood clotting factors.

Necessary for liver synthesis of plasma clotting factors II, VII, IX and X.

Can be assessed by measuring prothrombin tim

24
Q

Vitamin K deficiency

A

Haemorrhagic disease of the newborn:
-Vitamin K injection given to newborn babies

Rare in adults, unless on warfarin

25
Q

Vitamin K excess

A

K1 is relatively safe

Synthetic forms are more toxic

Can result in oxidative damage, red cell fragility and formation of methaemoglobin.

26
Q

Vitamin C is found in

A

Fresh fruit and vegetables

27
Q

Requirement of Vitamin C

A

40mg/day

28
Q

Functions of vitamin C

A

Collagen synthesis
Antioxidant
Iron absorption

29
Q

Deficiency of Vitamin C

A

Scurvy- easy bruising and bleeding, hair loss, teeth and gum disease

Treatment with vitamin C improves systems quickly

30
Q

Excess vitamin C

A

Doses > 1g/day can cause GI side effects

No evidence that increased vitamin C reduces the incidence or duration of colds.

31
Q

Vitamin B12 (Cobalamins) has 2 active forms

A

Methylcobalamin
5-deoxyadenosylcobalamin

32
Q

Vitamin B12 (Cobalamins)

A

Released from food by acid and enzymes in the stomach
Binds to R protein to protect it from stomach acid
Released from R proteins by pancreatic polypeptide.
Intrinsic factor (IF) produced by the stomach needed for absorption.
IF-B12 complex absorbed in the terminal ileum.
B12 is stored in the liver.

33
Q

Stored in

A

Fish, eggs, milk, meat

34
Q

Causes of vitamin B12 deficiency

A

Pernicious anaemia – autoimmune destruction of IF-producing cells in stomach.
Malabsorption – lack of stomach acid, pancreatic disease, small bowel disease.
Veganism

35
Q

Symptoms of Vitamin B12 deficiency

A

Macrocytic anaemia
Peripheral neuropathy in prolonged deficiency

36
Q

Folate

A

Folate is found in may foods fortified with folic acid.
Individuals have higher requirements in pregnancy.

37
Q

Functions of folate

A

Functions as a coenzyme in methylation reactions, DNA synthesis, synthesis of methionine from homocysteine.

38
Q

Causes of folate deficiency

A

Malabsorption
Drugs that interfere with folic acid metabolism (anticonvulsants, methotrexate)
Disease states that increase cell turnover (e.g. leukaemia, haemolytic anaemia, psoriasis)

39
Q

Symptoms of folate deficiency

A

High homocysteine levels
Macrocytic anaemia
Foetal development abnormalities (neural tube defects)

40
Q

Clotting factors

A

Intrinsic pathway activated by contact.
Extrinsic pathway activated by FVII coming in contact with tissue factor.
Initiates a cascade which ultimately results in fibrin clot formation.

41
Q

Clotting factors produced in the liver

A

I (Fibrinogen)
II (Prothrombin)
IV
V
VI
VII

42
Q

The performance of the clotting pathways can be measured using:

A

Prothrombin time (PT) (extrinsic pathway)
International normalised ratio (INR)
Activated partial thromboplastin time (aPTT) (intrinsic pathway)

43
Q

Prolonged PT

A

A prolonged PT may indicate a deficiency in the synthetic capacity of the liver.

Prolonged PT is not specific for liver disease:
-DIC
-Severe GI bleeding
-Some drugs
-Vitamin K deficiency

GI (16 decks)

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